Refining lubricating oil stock



July 8, 1941.

v W. E. FORNEY REFINING LUBRICATING OIL STOCK Filed July 9, lse

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Patented July 8, 1941 series;

VREFINING LUBRICATING OILv STO CK William E. Forney, Merchantville, N. J., assigner to Cities Service Oil Company, New York, N. Y., Y a corporation of Pennsylvania Application July 9, 1936, Serial-No. 89,714

8 Claims.

This invention relates to the refining of lubricating oil stocks and more particularly-to a process of rening Vlubricating oil stocks in which a selective solvent is employed for removing undesirable constituents.

In recent years lubricating oilI stocks have been rened by selectively removing certain undesirable constituents by the use of selective solvents instead of subjecting the oil to drastic treatment with concentrated sulfuric acid as commonly practiced in the past. Nitrobenzene, phenol and many other solvents have been proposed as a means for selectively removing certain constituents'from lubricating oil stocks. The present invention is an improvement in this type of process.

The primary object of the invention is to providev a processfor refining lubricating oil stocks by the use of a selective solvent adapted to selectively remove naphthenic and aromatic hydrocarbons as well as phenolic compounds from 1ubricating oil stocks. l

Accordingly, the improved process comprises the steps of intimately contactingthe oil to be refined with an alkylv sulfate (acid or normal) either alone or inl admixture with'sulfuric acid, continuing the contacting operation until theselective solvent `has absorbed the undesirable naphthenic and aromatic constituents, separatingV the solvent containing thev undesirable constituents fromthe purified oil and contacting the separated oil with a neutralizing agent;

Other features of the'improved process of the present invention will be apparent to those skilled in the art from the following more detailed description thereof takenfin connection with the accompanying drawing in which:

The single figure is a diagrammatic vertical view showing an apparatus particularly adaptedv for carrying out the improved process.

The alkyl sulfates used as a solvent in accordance with the present invention may be derived fromany suitable source, bui-,they may be made directly in connection withl the process by suitably treating olen gases with concentrated sulfurie acid. The olen gases used comprise individual olens or mixtures ofoleflns such as those obtained in the cracking of petroleum oils; A suitable mixture comprisesY cracking still gases containing ethylene, propylene, the butylenes and the amylenes.

The olen gases used to make the alkyl sulfates may be introduced into the apparatus shown in the drawing through a line 2, and

passed into the lowerportion of'` a contact tower 4. in intimate contact with concentrated sulfuric acid which may be introduced through a-line 6 and a cooler 8. The olefin gas mixture passes upwardly through a. tower and is brought in intimate-contact with the sulfuric acid which'ows downwardly over a series of bubble trays countercurrently to the gases. The acid is therefore gradually converted into alkyl sulfates so that by the time it reaches the bottom of the tower14. the acid mixture comprises sulfuricacid, acid -alkyl sulfates and a very substantial proportion `of dialkyl sulfates.

When treating afmixture of olefin gases inthe tower 4, the temperature is preferably controlled such that theolens higher boiling than ethylene are principally reacted with the acid. The temperature at the top of the 4tower 4 therefore should not be substantially above 50 F. while the temperature at the bottom of the tower is preferably held asllow as about 25 F. Where ethylene is treatedV alone for the manufacture of ethyl sulfate, the temperature at the top of the tower 4 should be about F., and the temperature at the bottom of the tower about 50 F. The tower 4 is provided with temperature control coils *I0 mounted in the liquid on each tray, and-each'coil is provided-with an individual supply line l2 which connects intoa mainline I4 for supplying a temperature control medium 4such as brine or. other fuid` at the proper temperature. The coils llldischarge through separate lines l6-into aline |48 from which the heat exchange medium may be sent to any desired point for temperature adi--v justrnent and then returned through the line l tothe coils I0.

The contact of the olefin gases withV concentrated sulfuric acid in the tower 4A necessarily produces a certain amount of polymerizationof the gaseous olelins to normally liquid products. Thisliquid material passes upwardly through thek tower 4 along with the unabsorbed gas andis dis'- chargedv with the unabsorbed gas through vva valved line 20 into a separator 22 in which the gas and liquid are separated. The gas is withdrawn from the separator 22 through a valvedv line 24, while the liquid is withdrawn throughA a valved line 26. The mixture of alkyl sulfates and sulfuric acid is withdrawn from the tower 4' -through a line 28 into a separator 3l) in which any hydrocarbon material present may be sepa-V rated and withdrawn through the ,valved line 32.

The alkyl sulfate or mixture of kalkyl sulfates and sulfuric acid to be used in the oil refining process is withdrawn from the separatori 30 through a line 34 and forced by means of a pump 36 through a line 38, a cooler 40 and one or more valved distribution lines 42, into the upper portion of a treating or extraction tower 44. Any sulfuric acid present may be removed from the alkyl sulfates in separator 30. The extraction tower 44 comprises a series of bubbler trays similar to that used in tower 4 and it also includes a cooling coil 46 mounted between each of the adjacent trays. Each of these coils 46 is supplied with a cooling fluid such as cold brine through individual valve supply lines 48 which connect with a main supply line 50. The coils 46 discharge through separate lines 52 into a main line 54.

The petroleum lubricating oil stock to be rened and which may be a distillate or residuum stock of a mixed base type is introduced into the extraction tower 44 (or other suitable contacting devices or chambers) through a valvedsupply line 56., Oil stock thus introduced is preferably diluted with a solvent such as liquid propane, butane, or pentane which will materially reduce the viscosity. and gravity of the oil. The oil may therefore comprise from 30% to 75% of such a hydrocarbon` diluent. This oil mixture introduced -through the linev 56 passes upwardly through the tower 44 and on each tray intimately contactsthe alkylsulfate extraction agent introduced through one or more of the lines 42 into the upper part of the tower. As the alkyl sulfate extraction agent passes downwardly through the tower it selectively removes from the diluted oil such Vconstituents as the naphthenic compounds, aromatic compounds and other compounds other than parain hydrocarbons. f This extracted materialtogether with the selective alkyl sulfate solvent-is discharged from the bottom of the tower through a valved line 58 and sent to a separaton 6l]l since the extracting agent may contain small proportions of the oil introduced through the line 56. The separated oil is removed through a line 62 and reintroduced into the tower 44, while the extract is withdrawn through a line 64.

The oil introduced into the tower 44 through the line 56 passes upwardly through the tower and out through a Valved line 66 into a separator 68. The separator 68 is used to remove any traces ofthe extracting agent which may be merely occluded in the oil. This extract is withdrawn from the separator through a line and introduced into the tower 44, while the separated oil is withdrawn through a line 12. It is to be understood that separators 22, 30, 60 and 68 may beV any type of normal gravity separator or centrifugal separator. In effecting the operation in tower 44, Ait is to be understood that suitable pressures may be maintained thereon to keep the liquid propane or other low boiling solvent in the liquid phase. Furthermore the temperatures in the` tower may be accurately controlled by means ofthe cooling coils 46. The temperatures actually used in carrying out the process will depend to a considerable extent upon the composition of the extracting medium employed.Y With normal sulfates only, the temperature may be as high as 140 to 150 F.; whereas if sulfuric acid is 'present the temperature should not exceed about 40 F. or a temperature sufficiently low to avoid polymerization. Where a mixture of normal and acid sulfates with sulfuric acid is used, a temperature of 32 F. or lower should be ernployed.

The diluted and extracted oil discharged through the line 'l2 (after removal of dissolved alkyl sulfate), is preferably brought in contact with some neutralizing agent such as fullers earth or other clay, and then dewaxed. In this connection, it will be noted that the oil is already diluted with liquid propane for example, and that the dewaxing operation may be effectively carried out by vaporizing a portion of the propane to effect the refrigeration necessary for precipitating the wax in the oil mixture. The oil may then be filtered or otherwise treated for the separation of the precipitated wax in accordance with well-known practice. 'Ihe clay or other alkaline treatment is particularly necessary where the extracting agent used in the tower 44 contains sulfuric acid.

Instead of carrying out the refining operation in the manner described above, the diluted lubricating oil stock may be treated simultaneously with the formation of alkyl sulfates in the tower 4. This may be accomplished by carrying out the operation described above in connection with tower 4 by introducing the diluted lubricating oil stock in at the base of the tower through a line 14 so that it enters the tower along with the olefin gas to be reactedwith the sulfuric acid. Under these circumstances the lubricating oil stock passes upwardly through the tower countercurrently to sulfuric acid and alkyl sulfates which pass downwardly through the tower. A suitable difference in'gravity between theV diluted oil and the extracting medium' is maintained to insure effective separation as the extraction proceeds. In this operation however, the lubricating oil stock discharged through the line 20 will have been contacted with concentrated sulfuric acid in the top of the tower, but this will have no detrimental effect upon the Aoil because of its dilution and because it contains substantially only paraftinic type hydrocarbons by the time it reaches the upper part of the tower 4 whereit contacts the strong sulfuric acid. The oil discharged into the separator`22 will be removed through the line 26, freed of occluded acid, and then'subjected to a clay treatment and dewaxing in the manner described above. Some oil may be separated out in' thefseparator 30 and discharged through the line 32. This should be added to the oil introduced through the line 14.

Where individual commercial extracting agents are to be used in the process, such for example as diethyl sulfate, diisopropyl sulfate, the butyl sulfates, the amyl sulfates, or the acid alkyl sulfates, the operation may be effectively carried out in the tower 44 by introducing the extracting agent into the top of the tower through a valved line 76. The operation then will be carried out in the manner described above in connection with the tower 44 except that'l in some cases it may be unnecessary, particularly where the neutral sulfates are used, to neutralize the extracted oil discharged through the line 66. In any case, however, any occluded sulfate should be removed from the oil by fullers earth, by hydrolysis and neutralization or by use of other solvents.

In order to thoroughly agitate the oil and extracting agent in the tower 44, any suitable gas may be introduced through line 18 and passed upwardly through the tower. This gas may be some inert gas which does not enter into reaction with any of the constituents in the tower. If any reaction is involved, such as in the use of olen gases and sulfuric acid, the temperatures must be Controlled. The line 18 may also be used for introducing additional diluent in any of the different modes of operation `described above. r

The pressure maintained inthe toWer *4. may vary from 75 to 250 lbs. per square inch in making the alkyl sulfates from oleiins, butwhen the diluted lubricating oil stock is introduced through the line 14 the pressure maybe maintained only sufficiently high to keep the diluent in the liquid phase at the temperatures employed. A pressure of at least about 100 lbs. per square inch is preferably used if alkyl sulfates are being made in the operation. The presence of the diluted lubricating oil stock 'in the tower 4 has a tendency toabsorb the oleiins and hold them in a position suitable for a controlled reaction with the sulfuric` acid. l

An extracting medium foru'se in the process, and comprising normal and acid sulfates and free sulfuric acid, may Ahave a specific gravity of approximately 1.318.- This extracting medium made from olefin gases for example, may be capable of producing approximately the following proportions of dry alcohols on hydrolysis: isopropyl 50%; butyl 30%; amyl 12%; hexyl 6%; higher alcohols 2%. The dialkyl sulfates used as extracting media almost without exception have a speciiic gravity greater than 1. The extracting agents used in accordance with the present invention, serve not only to remove undesirable constituents from the parainc type hydrocarbons, but in many cases actually alkylate some of the unsaturated constituents contained in the oil being extracted. Alkylation may also occur Where oleiins are introduced into contact with the oil in the presence of sulfuric acid. This results in the formation of a more parafiinic molecule from the unsaturated molecules and increases the yield of the rainate over that which would actually be obtained by the use of other extracting agents. The extracting agents of the present invention furthermore appear to make the resulting oil more readily de- Waxed; possibly by the removal of resinous types of compounds which appear to prevent crystalliZation of paraffin Wax. f The process is therefore particularly adapted in the treatment of long residuum or cylinder stock and can also be applied to the treatment of slop Wax distillates.

As an example of the use of the process and the properties of the treated oils, an original oil having a specific gravity of 0.988; a bromine number of 6.65; and a refractive index of 1.5505, gave a 40% yield of raflinate having a specific gravity of 0.940; a bromine number of 2.56; and a refractive index of 1.5285. The extracted oil in this example had a specific gravity of 1.045; a bromine number of 8.55; and a refractive index of 1.577. These results show a concentration of olens and aromatics in the extracted oil and a decrease in the specific gravity and refractive index for the raiiinate.

A further example of the operation of the process relates to the treatment of a dark green cylinder stock having a viscosity gravity constant (V. G. C.) of 0.87. The resulting product had a V. G. C. of 0.83; a color of 21/2 N. P. A., and a carbon residue of 0.38%. Oils of this viscosity (121 sec. Saybolt at 210 FJ, When refined by conventional methods, have a carbon residue of about 11/2 to 1%%, and a N. P. A. color of 8. The V. G. C. of 0.83 clearly marks the resulting product as primarily paranic in character. In another case, a neutral oil of 200 viscosity at 100 F. and having a V. G. C'. of 0.856 when treated by the process of the present invention, gave a raffinate having a V. G. C. of 0.832. The speciflc. gravity of this oil was decreased from 0.9059 to 0.8927, and therefractive index from 1.5004 17014872. The type of extracting media of the present invention appears to have exceptionally good selectivity for aromatic and unsaturated compounds.

From the foregoing description, it is apparent that various modifications may be made in the operation, and such is contemplated `Within the meaning of the appended claims.

Having thus described the invention what is claimed as new is:

1. In the art of rening petroleum lubricating oil stocks,l the process which comprises passing the voil stock to be refined through a series of contacting zones in one direction, introducing concentrated sulfuric acid into the last VZoneof the series, introducing a gas containing olefin into the iirst zone of the series, reacting the gas with the sulfuric acid to produce a mixture of alkyl sulfates and sulfuric acid, and passing the mixture counter-current to the oil through said series of zones to extract from the oil the non-paraiiinic constituents, discharging the extracted oil from the last zone of the series and discharging the alkyl sulfate extract from the iirst zone of the series.

2. In the art of reiining mineral oils, in which the mineral oil is extracted with a selective solvent for certain constituents of the oil, the improvement which comprises subjecting a mineral oil containing paraiiinic, naphthenic and aromatic hydrocarbons to the action of a selective solvent for the naphthenic and aromatic hydrocarbons of relatively high carbon-hydrogen ratio, said solvent comprising a mixture of alkyl sulfate, acid alkyl sulfate, and sulfuric acid in which the alkyl groups of the alkyl suliates contain not more than six carbon atoms, and separating the extract containing the naphthenic and aromatic hydrocarbons from the remainder of the oil.

3. In the art of refining mineral oils, the process which comprises separating an oil containing para'inic compounds and nonparainic compounds of the type of naphthenes and aromatics into fractions respectively richer in parain and non-parainic compounds by extracting said oil with a selective solvent for the naphthenic and aromatic hydrocarbons comprising an acid alkyl sulfate in which the alkyl group contains not more than six carbon atoms.

4. In the art of refining lubricating oil stocks containing paraiiinic, naphthenic and aromaticV hydrocarbons, the process which comprises diluting the oil stock with a liquefied normally gaseous hydrocarbon, passing the resulting mixture through a series of zones in which the temperature is controlled, passing an extracting agent comprising an acid alkyl sulfate having a selective solvent action for naphthenic and aromatic hydrocarbons counter-current through said zones to extract from the oil mixture the nonparainic hydrocarbons of the type of naphthenes and aromatics, and maintaining a superatmospheric pressure on said Zones suicient to retain said liquefied normally gaseous hydrocarbon in the liquid phase.

5. In the art of reiining mineral oil lubricating stocks, the process which comprises diluting the lubricating oil stock with a substantial proportion of liquefied normally gaseous hydrocarbons, separating such oil containing parafnic,

naphthenic and aromatic hydrocarbons into fractions respectively richer in paraiiinic and non-parafhnic compounds by extracting the oil with a selective solvent for naphthenic and aromatic hydrocarbons comprising an alkyl sulfate mixture produced by reacting a mixture of gaseous olens with sulfuric acid.

6. Ihe process of reining petroleum oi1 as dened by claim 1 in which the gas containing oleiin is intimately contacted with the sulfuric acid mixture in each zone to produce agitation of the sulfuric acid mixture and the oil being extracted.

7. In the art of refining petroleum lubricating oil stocks containing paranic and naphthenic hydrocarbons in which the naphthenic hydrocarbons are extracted from the lubricating oil stock in an extraction operation, the improvement which comprises dissolving the lubricating oil stock to be extracted and refined in a lique- :tied normally gaseous hydrocarbon diluent and passing the resulting dilutedmixture through a series of contacting zones in one direction, in-

troducing concentrated sulfuric acid into the last zone of the series and passing it through the series of zones countercurrent to the oil stock, introducing a mixture of gases containing olens into the rst zone of the series and passing them through the series of zones in intimate contact with the oil and the sulfuric acid under conditions adapted to react the olens with the acid to form alkyl sulfatos which are passed through the zones with any unreacted sulfuric acid to comprise an extracting medium for removing said naphthenic hydrocarbons from the oil, discharging the dilute extracted oil substantially free of naphthenic hydrocarbons from the last zone of the series and discharging the acid extract mixture containing the naphthenic hydrocarbons from the rst zone of the series.

8. The process as defined by claim 7 in which the dilute extracted oil discharged from the last zone of the series is contacted with a clay reiining agent to neutralize the oil.

WILLIAM E. FORNEY. 

